Sheet metal forming tool with a blank holder and tool sleeve with a force measuring device for transmitting the blank holder force

Abstract

Sheet metal forming tool (100) for use in a press, with a die (110), a punch (120) and a hold-down device (130), characterized in that a plurality of tool sleeves (140) arranged in the tool (100) are provided for transmitting the hold-down force to the hold-down device (130), wherein each of these tool sleeves (140) is equipped with a force measuring device (145) for measuring the sleeve force (F), such that the force measuring device (145) has two rings (146) fastened to the outer circumferential surface of the tool sleeve (140) and axially spaced apart, and a carrier plate (147) extending between these rings (146), on which carrier plate a measuring element (148) for force measurement is arranged.

Description

[0001] The invention relates to a sheet metal forming tool with a hold-down device according to the preamble of patent claim 1. The invention further relates to a tool sleeve for use in a sheet metal forming tool.

[0002] A sheet metal forming tool of this type is intended for use in a press (forming press) and comprises a die, a punch, and a blank holder that usually surrounds the punch. As is well known, the blank holder presses the edge zone of the sheet metal to be formed against the die during forming in order to influence the sheet draw-in and prevent wrinkling. The blank holder force required for this can be generated by a drawing device on the press, e.g., a table cushion or ram cushion, and is usually transferred to the blank holder via so-called sleeves. These sleeves are usually cylindrical pressure pins made of a steel alloy, for example, with a diameter of 60 mm, and are usually available as standardized machine elements (standard parts).

[0003] DE 41 12 656 A1 describes a drawing device in a press for drawing sheet metal parts. The blank holder force is applied via height-adjustable bolts (quills) that rest on a pressure plate (drawing cushion), with the bolts distributed over the entire surface of the blank holder. To ensure that the blank holder (6) is loaded with the required support force per bolt (7), each bolt (7) is additionally equipped with a force sensor (17).

[0004] The aforementioned state of the art provides for press-side measurement or recording of the respective quill (pressure) force. However, if a sheet metal forming tool is used in different presses, one would always have to rely on press-side force measurement, which is subject to press-specific fluctuations. The measurement results from different presses would therefore not be easily comparable.

[0005] The invention is intended to avoid or at least reduce at least one disadvantage associated with the prior art.

[0006] This is achieved with the sheet metal forming tool according to the invention in patent claim 1, which is in particular a deep-drawing tool. With the independent patent claim 6, the invention further extends to a tool sleeve (quill). Preferred developments and refinements of the invention arise analogously for all subject matter of the invention from the dependent patent claims, the following description of the invention, and the drawings.

[0007] The sheet metal forming tool according to the invention for use in a press comprises a die, a punch, and a blank holder, as well as several sleeves arranged in the sheet metal forming tool (and thus belonging to the sheet metal forming tool) for transmitting the blank holder force to or onto the blank holder. These sleeves can also be referred to as tool sleeves and are preferably attached to the blank holder. When the sheet metal forming tool is removed from a press, these sleeves remain in the sheet metal forming tool. Therefore, the same sleeves are always used in the sheet metal forming tool for transmitting or applying the blank holder force, so that production-related fluctuations, in particular in the sleeve lengths, do not need to be considered further.

[0008] The invention provides that each sleeve, i.e., all sleeves (tool sleeves) of the sheet metal forming tool according to the invention, are each equipped with (at least) one force measuring device for measuring the respective sleeve (pressure) force. This enables tool-side and press-independent measurement or recording of the sleeve forces as well as the load distribution (which refers to the distribution of the total blank holder force to be transmitted among the individual sleeves). This can accelerate tool training. Furthermore, control, in particular real-time control, of the load distribution during ongoing press operation is enabled.

[0009] The sheet metal forming tool according to the invention can accommodate at least one electric generator for supplying current and / or voltage to the force-measuring devices, which is activated particularly during the tool closing and opening movements. A wired external power supply can thus be eliminated. Alternatively, each sleeve can be equipped with a piezoelectric generator (piezo generator) for supplying current and / or voltage to the respective force-measuring device. The piezoelectric generator is preferably integrated directly into the force flow through the sleeve.

[0010] In the sheet metal forming tool according to the invention, measuring and / or evaluation electronics for the measurement evaluations can also be arranged, in particular on the blank holder. Furthermore, at least one measuring amplifier can also be arranged in the sheet metal forming tool. External cabling can thus be omitted (tool-external communication can take place, for example, via WLAN). The power supply can be provided by means of the electric generator (see above). The force measuring devices can be connected to the measuring amplifier or the measuring and / or evaluation electronics via cable connections or wirelessly. The measuring and / or evaluation electronics is preferably a component of a (multifunctional) control unit for the sheet metal forming tool that is installed in the sheet metal forming tool.

[0011] A quill (tool quill) for use in a sheet metal forming tool according to the invention is equipped with (at least) one force measuring device for measuring the quill force.

[0012] The force measuring device can comprise at least one strain gauge (SG), a piezoresistive sensor (force sensor), and / or an electroactive polymer-based EAP sensor. For the functionality of these measuring elements or sensors, please refer to the relevant specialist literature. The measuring elements or sensors can be applied, in particular glued, directly to the outer surface or outer circumferential surface of the sleeve. Furthermore, the measuring elements or sensors can be applied as a coating, in particular as a piezoresistive coating or as a coating made of an electroactive polymer, directly to the outer surface or outer circumferential surface of the sleeve. Both variants are also suitable for retrofitting.

[0013] The force measuring device preferably has two rings fastened to the lateral surface or outer circumferential surface of the quill and spaced apart in the axial direction of the quill, as well as at least one carrier plate or the like extending between the rings, in particular extending in the axial direction of the quill, on which (at least) one measuring element or one measuring sensor, in particular of the type mentioned above, is arranged for force measurement. The force measurement takes place in a secondary force flow. This variant is also suitable for retrofitting. The rings are preferably detachably fastened to the quill by means of space-saving threaded pins (grub screws), whereby the rings can each have at least one corresponding radial bore (for the threaded pin).

[0014] The quill can be designed with at least one groove, bore, or the like for the wiring of the force measuring device and / or a piezoelectric generator (see above). The (wired) groove can be sealed with a resin compound or the like.

[0015] Preferably, such a sleeve (tool sleeve) provided with a force measuring device is used in a sheet metal forming tool (of the type mentioned above), in particular in a deep-drawing tool. Preferably, all sleeves of the sheet metal forming tool are equipped with a corresponding force measuring device and in particular are fastened to the blank holder (and are thus components of the sheet metal forming tool). Each of these sleeves can be assigned a motor-operated wedge slide or the like in order to be able to change the effective sleeve length and thereby the load distribution (i.e. the distribution of the total blank holder force to be transmitted across the individual sleeves). Preferably, the load distribution is changed in a control loop, wherein the sleeve force (partial load) transmitted by each sleeve is measured with the aid of the force measuring devices and, if necessary, adjusted by changing the effective sleeve length.To ensure the required sheet metal part quality, this can also be done during ongoing press or tool operation. The control can be accomplished by a control unit (see above), which may also communicate with the press control system.

[0016] The invention is explained in more detail below by way of example and in a non-limiting manner with reference to the drawings. The features shown in the figures of the drawings and / or explained below may, even independently of specific combinations of features, be general features of the invention and may further develop the invention accordingly. Fig. 1 shows a schematic section of a sheet metal forming tool. Fig. 2 shows in two individual representations a preferred embodiment of a sleeve with a force measuring device for use in the sheet metal forming tool of Fig. 1.

[0017] The Fig. The sheet metal forming tool 100 shown in Figure 1 is intended for use in a press and comprises a die 110, a punch 120, and a blank holder 130 surrounding the punch 120. The blank holder force is applied to the blank holder 130 or transferred to the blank holder 130 by means of several sleeves 140. The sleeves 140 are attached to the blank holder 130, in particular screwed to the blank holder 130, and extend partially through bores 155. According to the invention, the sleeves 140 are each provided with a force measuring device 145 (see Fig. 2) equipped to measure the respective quill force.

[0018] Fig. Figure 2 shows a preferred embodiment of such a sleeve 140. The sleeve 140, designed as a cylindrical pressure pin 141, has a plate-like flange 142 for attachment to the hold-down device 130. The force measuring device 145 for measuring the sleeve force comprises two sleeve-like or clamp-like rings 146 attached to the lateral surface or outer circumferential surface of the pin 141, which are spaced apart from one another in the axial direction of the sleeve 140, as well as a carrier plate 147 extending axially from one ring 146 to the other ring 146, on which at least one measuring element or measuring sensor 148 is arranged. The measuring element or measuring sensor 148 is, for example, a strain gauge (SG), a piezoresistive sensor (force sensor), and / or an EAP sensor based on electroactive polymer technology. Preferably, there is an air gap between the carrier plate 147 and the outer peripheral surface of the bolt 141.However, the carrier plate 147 can also rest on the outer peripheral surface of the bolt 141.

[0019] The support plate 147 can be welded or soldered to the rings 146, whereby a one-piece construction of the support plate 147 and the rings 146 is also possible. In the embodiment shown, the support plate 147 is arranged between the rings 146, so that the force transmission or force introduction into the support plate 147 takes place via the mutually facing, axial end faces of the rings 146.

[0020] The force measurement is carried out in a secondary force flow, in that the compression of the bolt 141 under pressure is transferred via the rings 146 to the carrier plate 147 (the carrier plate 147 is also compressed, as in Fig.2b by the arrows F and F') and is recorded there using the measuring element or measuring sensor 148. The sleeve force can then be determined (e.g., by comparison with previous reference measurements) or calculated from the recorded deformation of the carrier plate 147. The rings 146 are detachably attached to the sleeve 140 or to the bolt 141 via the radial bores 149 using threaded pins (grub screws). The force measuring device 145 is designed to be as flat as possible in the radial direction, ensuring the free movement of the sleeve 140 in the bore 155. List of reference symbols 100 sheet metal forming tools 110 die 120 stamps 130 hold-down clamps 140 quill 141 bolts (base body) 142 flange 145 force measuring device 146 rings 147 Carrier plate 148 measuring element, measuring sensor 149 Radial bore (fastening) 150 base plate 155 bore F quill force F' measuring force

Claims

[1] Sheet metal forming tool (100) for use in a press, comprising a die (110), a punch (120) and a hold-down device (130), characterized by that a plurality of tool sleeves (140) arranged in the tool (100) are provided for transmitting the hold-down force to the hold-down device (130), each of these tool sleeves (140) being equipped with a force measuring device (145) for measuring the sleeve force (F), such that the force measuring device (145) has two rings (146) fastened to the outer circumferential surface of the tool sleeve (140) and axially spaced apart, and a carrier plate (147) extending between these rings (146), on which carrier plate a measuring element (148) for force measurement is arranged. [2] Sheet metal forming tool (100) according to claim 1, characterized by that the tool sleeves (140) are attached to the hold-down device (130). [3] Sheet metal forming tool (100) according to claim 1 or 2, characterized bythat an electrical generator actuated by the tool movements is arranged in the tool (100) for supplying current and / or voltage to the force measuring devices (145). [4] Sheet metal forming tool (100) according to claim 1 or 2, characterized by that each tool sleeve (140) is equipped with a piezoelectric generator for supplying current and / or voltage to the respective force measuring device (145). [5] Sheet metal forming tool (100) according to one of the preceding claims, characterized by that measuring electronics for the measurement evaluations are arranged in the tool (100). [6] Tool sleeve (140) for use in a sheet metal forming tool (100) according to one of the preceding claims, characterized bythat the tool sleeve (140) is equipped with a force measuring device (145) for measuring the sleeve force (F), wherein the force measuring device (145) has two rings (146) fastened to the outer circumferential surface of the tool sleeve (140) and axially spaced apart, and a carrier plate (147) extending between these rings (146), on which a measuring element (148) for force measurement is arranged. [7] Tool sleeve (140) according to claim 6, characterized by that the rings (146) are detachably fastened to the tool sleeve (140) by means of threaded pins. [8] Tool sleeve (140) according to claim 6 or 7, characterized by a groove or hole for the wiring of the force measuring device (145).

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